Email cant log into new ISPconfig 3 installation

Ok I am hearing that the users should log in with client_username but where do I find that information for what exact client name they are when I am only a reseller? I have tried what I think it would be but it doesn't work. I am guessing it should be something like web9_username but the logs show that it is getting a permissions error when doing so. What is the correct way to do this. No one can check their mail even though they seem to be getting it on the server.